In May 2013, while serving a warrant, sheriff's deputies discovered them inside a room at the Knights Inn in St. Petersburg. Detectives arrested four people accused of running a human trafficking ring. The teens, both runaways, were placed in foster care after their parents said they didn't want them back.

It was the first case handled by the Special Victims Unit, formed by the Pinellas County Sheriff's Office to crack down on local human trafficking and sex exploitation cases. More than a year after forming, the unit is busy: its six detectives typically handle more than 10 cases each.

"We were seeing more and more of this type of activity. . . . The question became: Are we seeing an increase of it, or uncovering more of what's happening?" said Sheriff Bob Gualtieri. "Young girls and boys that are basically enslaved to engage in sex acts so other people can make money off of them."

The FBI Tampa field office, which covers 18 counties, including Pinellas, Hillsborough, Pasco, and Hernando, has also handled a plethora of child sex trafficking cases. Since 2009, the FBI Central Florida Crimes Against Children Task Force has rescued nearly 200 juveniles, said special agent Dave Couvertier, agency spokesman.

"Law enforcement is getting better at investigating these matters," he said. "People are realizing that human trafficking actually exists in the United States, that it occurs within our local communities."

At the Sheriff's Office, the Special Victims Unit got started with Sgt. Kurt Romanosky and two or three detectives in April 2013. By January, the unit was fully staffed with Romanosky, six detectives and a crime analyst.

Their human trafficking-related arrests include the arrest of Wanda Ann Ringgo, accused in November of prostituting a 14-year-old foster girl who was forced to have sex with a man, the Sheriff's Office said. The unit also assisted in the federal arrests of Gerald Eugene Mayham, 41, and Joel Raymond Nauta, 23, accused in February of prostituting a 16-year-old at a Clearwater apartment complex.

Gualtieri said the Sheriff's Office has received tips about businesses that may be exploiting immigrants who were "brought here and basically enslaved."

Special Victims detectives also investigate child predators because, just as traffickers, they tend to find victims online on websites such as Backpage.com, Romanosky said. Child pornography cases are also among the unit's workload.

Among the trends the Sheriff's Office and the FBI have discovered: sex traffickers have typically dabbled in other crimes, including drug dealing.

For example, Antron Smith, 31, and Donell Jenkins, 22, both charged in connection with the Knights Inn case, have been previously convicted of selling cocaine and violated their probations when they were arrested in May 2013.

"We're clamping down on the pill mills and drug trafficking," Gualtieri said. "A lot of the same people are migrating from one illegal enterprise to another."

Among the challenges in investigating human trafficking is getting victims to talk, Romanosky said.

"There's not a trust with law enforcement yet," he said. "Honestly, sometimes, there's nothing you can say. Sometimes, they will tune you out. You have to talk to them multiple times."

In Ringgo's case, the victim, who is related to her, asked prosecutors to seek a lesser charge. Last month, Ringgo, 60, was sentenced to 18 months in prison after she pleaded guilty to child abuse.

"Her wishes needed to be considered," said Assistant State Attorney Holly Grissinger, adding that besides a welfare fraud conviction in 1980, Ringgo "had no other criminal history of any kind. We had no complaints about her."

Many victims are also "programmed" by their traffickers to distrust police, Couvertier said, adding some victims have gone as far as to spit at investigators.

"The investigators that do this are very dedicated," he said. "They really believe in what they're doing."